use super::cpu::{Cpu, RegisterPair}; pub enum Instruction { NOP, LD(LDTarget, LDTarget), STOP, JR(JumpCondition, i8), ADD(MATHTarget, MATHTarget), INC(AllRegisters), DEC(AllRegisters), RLCA, RRCA, RLA, RRA, DAA, CPL, SCF, CCF, HALT, ADC(MATHTarget, MATHTarget), SUB(MATHTarget), // SUB A, MATHTarget always SBC(MATHTarget, MATHTarget), AND(MATHTarget), // AND A, MATHTarget always XOR(MATHTarget), // XOR A, MATHTarget always OR(MATHTarget), // OR A, MATHTarget always CP(MATHTarget), // CP A, MATHTarget always RET(JumpCondition), LDHL(i8), // LD HL, SP + d POP(RegisterPair), RETI, JP(JumpCondition, JPTarget), DI, EI, CALL(JumpCondition, u16), PUSH(RegisterPair), RST(u8), } impl Instruction { pub fn from_byte(cpu: &Cpu, byte: u8) -> Self { if byte == 0xCB { Self::from_prefixed_byte(cpu, byte) } else { Self::from_unprefixed_byte(cpu, byte) } } fn from_prefixed_byte(cpu: &Cpu, opcode: u8) -> Self { // https://gb-archive.github.io/salvage/decoding_gbz80_opcodes/Decoding%20Gamboy%20Z80%20Opcodes.html let x = (opcode >> 6) & 0b00000011; let y = (opcode >> 3) & 0b00000111; let z = opcode & 0b00000111; let p = y >> 1; let q = y & 0b00000001; let n = cpu.read_byte(cpu.register_pair(RegisterPair::PC) + 1); let nn = cpu.read_word(cpu.register_pair(RegisterPair::PC) + 1); match (x, z, q, y, p) { (0, 0, _, 0, _) => Instruction::NOP, // NOP (0, 0, _, 1, _) => Instruction::LD( // LD (nn), SP LDTarget::ByteAtAddress(nn), LDTarget::RegisterPair(RegisterPair::SP), ), (0, 0, _, 2, _) => Instruction::STOP, // STOP (0, 0, _, 3, _) => Instruction::JR(JumpCondition::Always, n as i8), // JR d (0, 0, _, 4..=7, _) => Instruction::JR(Table::cc(y - 4), n as i8), // JR cc[y - 4], d (0, 1, 0, _, _) => Instruction::LD( // LD rp[p], nn LDTarget::RegisterPair(Table::rp(p)), LDTarget::ImmediateWord(nn), ), (0, 1, 1, _, _) => Instruction::ADD( // ADD HL, rp[p] MATHTarget::HL, MATHTarget::RegisterPair(Table::rp(p)), ), (0, 2, 0, _, 0) => Instruction::LD( // LD (BC), A LDTarget::IndirectRegister(InstrRegisterPairs::BC), LDTarget::Register(InstrRegisters::A), ), (0, 2, 0, _, 1) => Instruction::LD( // LD (DE), A LDTarget::IndirectRegister(InstrRegisterPairs::DE), LDTarget::Register(InstrRegisters::A), ), (0, 2, 1, _, 0) => Instruction::LD( // LD A, (BC) LDTarget::Register(InstrRegisters::A), LDTarget::IndirectRegister(InstrRegisterPairs::BC), ), (0, 2, 1, _, 1) => Instruction::LD( // LD A, (DE) LDTarget::Register(InstrRegisters::A), LDTarget::IndirectRegister(InstrRegisterPairs::DE), ), (0, 2, 0, _, 2) => Instruction::LD( // LD (HL+), A LDTarget::IndirectRegister(InstrRegisterPairs::IncrementHL), LDTarget::Register(InstrRegisters::A), ), (0, 2, 0, _, 3) => Instruction::LD( // LD (HL-), A LDTarget::IndirectRegister(InstrRegisterPairs::DecrementHL), LDTarget::Register(InstrRegisters::A), ), (0, 2, 1, _, 2) => Instruction::LD( // LD A, (HL+) LDTarget::Register(InstrRegisters::A), LDTarget::IndirectRegister(InstrRegisterPairs::IncrementHL), ), (0, 2, 1, _, 3) => Instruction::LD( // LD A, (HL-) LDTarget::Register(InstrRegisters::A), LDTarget::IndirectRegister(InstrRegisterPairs::DecrementHL), ), (0, 3, 0, _, _) => Instruction::INC( // INC rp[p] AllRegisters::Word(Table::rp(p)), ), (0, 3, 1, _, _) => Instruction::DEC( // DEC rp[p] AllRegisters::Word(Table::rp(p)), ), (0, 4, _, _, _) => Instruction::INC( // INC r[y] AllRegisters::Byte(Table::r(y)), ), (0, 5, _, _, _) => Instruction::DEC( // DEC r[y] AllRegisters::Byte(Table::r(y)), ), (0, 6, _, _, _) => Instruction::LD( // LD r[y], n LDTarget::Register(Table::r(y)), LDTarget::ImmediateByte(n), ), (0, 7, _, 0, _) => Instruction::RLCA, (0, 7, _, 1, _) => Instruction::RRCA, (0, 7, _, 2, _) => Instruction::RLA, (0, 7, _, 3, _) => Instruction::RRA, (0, 7, _, 4, _) => Instruction::DAA, (0, 7, _, 5, _) => Instruction::CPL, (0, 7, _, 6, _) => Instruction::SCF, (0, 7, _, 7, _) => Instruction::CCF, (1, 6, _, 6, _) => Instruction::HALT, (1, _, _, _, _) => Instruction::LD( // LD r[y], r[z] LDTarget::Register(Table::r(y)), LDTarget::Register(Table::r(z)), ), (2, _, _, _, _) => Table::x2_alu(y, z), // alu[y] r[z] (3, 0, _, 0..=3, _) => Instruction::RET(Table::cc(y)), // RET cc[y] (3, 0, _, 4, _) => Instruction::LD( // LD (0xFF00 + n), A LDTarget::ByteAtAddress(0xFF00 + (n as u16)), // TODO: Do we want to do any calculations here? LDTarget::Register(InstrRegisters::A), ), (3, 0, _, 5, _) => Instruction::ADD( // ADD SP, d MATHTarget::RegisterPair(RegisterPair::SP), MATHTarget::ImmediateByte(n), ), (3, 0, _, 6, _) => Instruction::LD( // LD A, (0xFF00 + n) LDTarget::Register(InstrRegisters::A), LDTarget::ByteAtAddress(0xFF00 + (n as u16)), // TODO: DO we want to do any calculations here? ), (3, 0, _, 7, _) => Instruction::LDHL(n as i8), // LD HL, SP + d (3, 1, 0, _, _) => Instruction::POP(Table::rp2(p)), // POP rp2[p] (3, 1, 1, _, 0) => Instruction::RET(JumpCondition::Always), // RET (3, 1, 1, _, 1) => Instruction::RETI, (3, 1, 1, _, 2) => Instruction::JP( // JP HL JumpCondition::Always, JPTarget::RegisterPair(RegisterPair::HL), ), (3, 1, 1, _, 3) => Instruction::LD( // LD SP, HL LDTarget::RegisterPair(RegisterPair::SP), LDTarget::RegisterPair(RegisterPair::HL), ), (3, 2, _, 0..=3, _) => Instruction::JP( // JP cc[y], nn Table::cc(y), JPTarget::ImmediateWord(nn), ), (3, 2, _, 4, _) => Instruction::LD( // LD (0xFF00 + C) ,A LDTarget::Register(InstrRegisters::IndirectC), LDTarget::Register(InstrRegisters::A), ), (3, 2, _, 5, _) => Instruction::LD( // LD (nn), A LDTarget::ByteAtAddress(nn), LDTarget::Register(InstrRegisters::A), ), (3, 2, _, 6, _) => Instruction::LD( // LD A, (0xFF00 + C) LDTarget::Register(InstrRegisters::A), LDTarget::Register(InstrRegisters::IndirectC), ), (3, 2, _, 7, _) => Instruction::LD( // LD A, (nn) LDTarget::Register(InstrRegisters::A), LDTarget::ByteAtAddress(nn), ), (3, 3, _, 0, _) => Instruction::JP( // JP nn JumpCondition::Always, JPTarget::ImmediateWord(nn), ), (3, 3, _, 1, _) => unreachable!("This is the 0xCB Prefix"), // (3, 3, _, 2, _) => unreachable!(), (removed in documentation) // (3, 3, _, 3, _) => unimplemented!(), (removed in documentation) // (3, 3, _, 4, _) => unimplemented!(), (removed in documentation) // (3, 3, _, 5, _) => unimplemented!(), (removed in documentation) (3, 3, _, 6, _) => Instruction::DI, (3, 3, _, 7, _) => Instruction::EI, (3, 4, _, 0..=3, _) => Instruction::CALL(Table::cc(y), nn), // CALL cc[y], nn // (3, 4, _, 4..=7, _) => unimplemented!(), (removed in documentation) (3, 5, 0, _, _) => Instruction::PUSH(Table::rp2(p)), // PUSH rp2[p] (3, 5, 1, _, 0) => Instruction::CALL(JumpCondition::Always, nn), // CALL nn // (3, 5, 1, _, 1..=3) => unimplemented!(), (removed in documentation) (3, 6, _, _, _) => Table::x3_alu(y, n), (3, 7, _, _, _) => Instruction::RST(y * 8), // RST y * 8 _ => unimplemented!( "Unknown Opcode: {:#?}\n x: {}, z: {}, q: {}, y: {}, p: {}", opcode, x, z, q, y, p ), } } fn from_unprefixed_byte(cpu: &Cpu, byte: u8) -> Self { unimplemented!() } } pub enum JPTarget { RegisterPair(RegisterPair), ImmediateWord(u16), } pub enum AllRegisters { Byte(InstrRegisters), Word(RegisterPair), } pub enum MATHTarget { HL, SP, Register(InstrRegisters), RegisterPair(RegisterPair), ImmediateByte(u8), } pub enum LDTarget { Register(InstrRegisters), IndirectRegister(InstrRegisterPairs), ByteAtAddress(u16), ImmediateWord(u16), ImmediateByte(u8), RegisterPair(RegisterPair), } enum InstrRegisterPairs { AF, BC, DE, HL, SP, PC, IncrementHL, DecrementHL, } enum InstrRegisters { A, B, C, D, E, H, L, IndirectHL, // (HL) IndirectC, // (0xFF00 + C) } pub enum JumpCondition { NotZero, Zero, NotCarry, Carry, Always, } struct Table; impl Table { pub fn r(index: u8) -> InstrRegisters { match index { 0 => InstrRegisters::B, 1 => InstrRegisters::C, 2 => InstrRegisters::D, 3 => InstrRegisters::E, 4 => InstrRegisters::H, 5 => InstrRegisters::L, 6 => InstrRegisters::IndirectHL, 7 => InstrRegisters::A, _ => unreachable!("Index {} is out of bounds in r[]", index), } } pub fn rp2(index: u8) -> RegisterPair { match index { 0 => RegisterPair::BC, 1 => RegisterPair::DE, 2 => RegisterPair::HL, 3 => RegisterPair::AF, _ => unreachable!("Index {} out of bounds in rp2[]", index), } } pub fn rp(index: u8) -> RegisterPair { match index { 0 => RegisterPair::BC, 1 => RegisterPair::DE, 2 => RegisterPair::HL, 3 => RegisterPair::SP, _ => unreachable!("Index {} out of bounds in rp[]", index), } } pub fn cc(index: u8) -> JumpCondition { match index { 0 => JumpCondition::NotZero, 1 => JumpCondition::Zero, 2 => JumpCondition::NotCarry, 3 => JumpCondition::Carry, _ => unreachable!("Index {} out of bounds in cc[]", index), } } pub fn x2_alu(fn_index: u8, r_index: u8) -> Instruction { match fn_index { 0 => Instruction::ADD( // ADD A, r[z] MATHTarget::Register(InstrRegisters::A), MATHTarget::Register(Self::r(r_index)), ), 1 => Instruction::ADC( // ADC A, r[z] MATHTarget::Register(InstrRegisters::A), MATHTarget::Register(Self::r(r_index)), ), 2 => Instruction::SUB(MATHTarget::Register(Self::r(r_index))), // SUB r[z] 3 => Instruction::SBC( // SBC A, r[z] MATHTarget::Register(InstrRegisters::A), MATHTarget::Register(Self::r(r_index)), ), 4 => Instruction::AND(MATHTarget::Register(Self::r(r_index))), // AND r[z] 5 => Instruction::XOR(MATHTarget::Register(Self::r(r_index))), // XOR r[z] 6 => Instruction::OR(MATHTarget::Register(Self::r(r_index))), // OR r[z] 7 => Instruction::CP(MATHTarget::Register(Self::r(r_index))), // CP r[z] _ => unreachable!("Index {} is out of bounds in alu[]"), } } pub fn x3_alu(fn_index: u8, byte: u8) -> Instruction { unimplemented!() } }